Aerobically unstable ensiled forages:
An avoidable loss
Tony Hall and Bob Charley for Progressive Dairyman
Ensiling forages, an age-old
process, comes with both unavoidable
and avoidable losses of nutrients. With
corn at $6 per bushel and soy beans
at $12 per bushel, the market value
of corn silage based on its nutrient
content is in excess of $70 per ton as
fed or $200 per ton dry matter for a 35
percent dry matter crop – we clearly
need to pay closer attention to the
avoidable losses.
Avoidable on-farm shrink or dry
matter losses in the ensilage process
can have significant financial impact
on the bottom line. For example, 1,000
tons of bunk silage at 35 percent dry
matter with a 10 percent dry matter
reduction overall will lose 35 tons
of silage dry matter. This lost feed is
conservatively worth more than $7,000
(35 x $200). This loss of dry matter
and nutrients from corn silage has to
be made up from other sources. Even
Table 1
Process
worse, it is the very digestible fraction
that is lost (sugars, low molecular
weight polysaccharides, volatile fatty
acids and lactic acid), so the silage
does not feed as well and even more
expensive grain has to be fed to
maintain production.
There are many sources of dry
matter loss in the ensilage process,
summarized in Table 1. Some of these
are unavoidable even with modern
silage-making practices but, by far,
the largest potential source of dry
matter losses are related to aerobic
deterioration, and these need to be
managed to avoid high losses during
storage and feedout.
While many dairy farms use an
effective inoculant to promote a good
front-end homolactic fermentation,
most are losing highly valuable
digestible dry matter from the silo
(bunk, pile, bag bale or tower) once
Summary of silage-making dry matter energy
losses and the main causative factors*
Typical
Classification
Loss
Causative Factor
(%)
Field wilting
Unavoidable
2 to 5
Weather, crop,
technique
Fermentation
Unavoidable
2 to 4
Microbes
Residual respiration
Unavoidable
1 to 2
Plant enzymes
Secondary
fermentation
(Clostridia)
Avoidable
0 to 5
Delayed filling, low DM
content, soil
Aerobic loss in silo
Avoidable
0 to 10
Delayed filling, poor
packing, high DM crop,
poor sealing
Aerobic loss at feedout
Avoidable
0 to 15
As with “in silo” above,
poor face management,
too slow feedout rate,
summer season
*(Adapted from: McDonald, et al., 1991)
Table 2
Selected initial characteristics of chopped
corn silage before ensiling, (1999-2001)*
1999
2000
2001
% dry matter
32.7
45.8
36.7
pH
5.90
5.98
5.79
Indigenous yeasts
(log (cfu/g))
6.28
8.02
7.40
*(Adapted from Muck, 2004)
the product is exposed to air (oxygen)
and feedout begins. This process of
aerobic deterioration is exacerbated
by warmer temperatures, especially
in the summer. Well-fermented crops
with low terminal pH’s and high lactic
acid contents that were cool in winter
are then prone to heating and aerobic
instability at the bunk face, in drop
piles and in TMR’s. Unless active
management decisions are taken, high
financial losses are imminent.
The wild yeast content
of crops for ensilage
A starting point for understanding
aerobic instability is the indigenous
(wild), microbial profile of crops
taken for ensilage. A typical example
is shown in Table 2 for corn silage
crops in Wisconsin sampled over three
years prior to ensilage. Although we
cannot see them with the naked eye,
every gram (0.002 pounds) of standing
forage contains anywhere from 10,000
to 100,000,000 colony forming units
(CFU) of indigenous (spoilage) yeasts.
From Table 2 it can be noted that a
stressed crop, taken too late, has high
wild yeast counts (e.g., year 2000).
These wild spoilage yeasts, an
occupational hazard of the silage
storage and feedout processes,
were first noted in 1932. The role of
wild spoilage yeasts in the aerobic
deterioration of ensiled crops became
increasingly understood through the
period of 1964 to 1990. Wild yeasts
belong to the Fungi kingdom (as do
molds) but, unlike molds, wild spoilage
yeasts are nonpathogenic and are not
known to produce toxic secondary
metabolites. They are predominantly
aerobic, meaning they require oxygen
to grow. This means once the packing
and sealing process is complete and
anaerobic conditions are achieved in
the silage bunk, bag or tower, wild
spoilage yeasts inside the ensiled crop
will be dormant and inactive. Wild
yeasts can also be found in equally
large numbers on small-grain silage
crops, alfalfa and grass silages.
There is a wide range of wild
spoilage yeasts represented in standing
forages, but those of main concern are
the lactic acid fermenting species of
Candida, Hensenula and Pichia. Once
exposed to oxygen (through opening
the silo or bag), these fermentative
spoilage yeasts can use the lactic acid
in the silage as an energy source,
generating heat, carbon dioxide gas
and water, almost literally burning
up dry matter unless preventative
measures are taken.
In warmer temperatures (65°F
plus), the spoilage yeast population
can double every two hours, causing
heating and local pH increases,
allowing aerobic spoilage by molds
and bacteria, plus massive digestible
dry matter loss. Typical yeast spoilage
problems can be identified at the
feedout face using two silage probes,
one at three-foot depth and the other
just six inches. After 10 seconds the
temperatures can be compared – as
seen in the photo below. In this
example, the heating due to spoilage
yeasts is evident with a 35°F increase
near the surface compared to further
back in the bunk.
In the summer, the yeast
spoilage challenge increases and
cow performance can be greatly
compromised. The unstable silage
or haylage may only be stable for a
few hours either on the face or in the
drop-down pile before making the
TMR. Once unstable forages are mixed
in the TMR, spoilage yeasts have more
nutrients and more time to multiply,
even in a 2x mixing operation.
The keeping quality of the TMR is
compromised, transition cows are
challenged and either milk production
or milk fat is reduced. In studies with
spoiled high-moisture shell corn added
to a TMR, average daily milk yield
was reduced by three pounds per cow
within 14 days.
While the farm can resort to
adding TMR stabilizing products to
try to keep the feed stable, these do
not address the spoilage yeast load
in the parent forages, nor the dry
matter losses caused in the silage itself.
Furthermore, the TMR stabilizers
are not cheap at the recommended
Continued on back page
PO Box 585 • Jerome, ID 83338-0585 • 208.324.7513 or 800.320.1424 • Fax 208.324.1133
Aerobically unstable ensiled forages: An avoidable loss, cont’d from front
application rates, costing in the range
of 15-20 cents per milk cow daily.
Taking control
A greater financial return on
converting silage crops to milk can be
achieved with a more comprehensive
forage plan that targets reduced dry
matter losses from field to feedout.
Key steps are detailed below:
•Cut at the right growth stage and
target dry matter range for the crop.
• Short but effective wilting periods;
haylage in a day.
• At chopping use a U.S. university-
researched and industry-proven
inoculant combination that
contains the strain effective rate for
Lactobacillus buchneri (FDA-reviewed
claim for use at 400,000 CFU per
gram on silage, 600,000 CFU per
gram on high-moisture corn). This
will generate acetic acid to control the
spoilage yeasts and keep the product
cool and stable at point of feeding.
“
• Pack silos quickly and ensure a
While many dairy farms use an
effective inoculant to promote
a good front-end homolactic
fermentation, most are losing
highly valuable digestible dry
matter from the silo (bunk, pile,
bag bale or tower) once the
product is exposed to air (oxygen)
and feedout begins.
packing density of no less than 16
pounds of forage dry matter per cubic
foot.
• Seal effectively all over – sides, top
and at the front toe.
• Once bunk or bag is open, move
through it quickly to minimize face
exposure to air (six to 12 inches
in cool weather, 12 to 18 inches in
summer with smaller faces exposed).
• Do not move top sheet and tires
back too far at any one time.
• Keep face smooth with dexterous
use of loader bucket – no lifting to let
air in. Investment in silage defacer?
• Minimize time between taking
down face and mixing in the TMR; do
not pile ahead too much.
A good silage-making plan to
control aerobic spoilage will include
an effective silage inoculant based
on a proven L. buchneri strain at
the effective dose level. This is the
cost-effective way to address the
ongoing challenge of indigenous
aerobic spoilage yeasts on silage
heating, associated dry matter loss
and depressed milk component yield.
By actively managing the entire
ensiling process, you can keep that
”
$7,000 of avoidable loss in your pocket.
Definitely a case where prevention
pays! PD
Co-author Bob Charley is employed
as a forage products manager at
Lallemand Animal Nutrition.
References omitted due to space
but are available upon request.
Reprinted from Apr. 11, 2012
Tony Hall
Dairy Technical
Services Manager
Lallemand Animal
Nutrition
[email protected]
Temperature probes indicating heating and yeast activity on the silo face.
PO Box 585 • Jerome, ID 83338-0585 • 208.324.7513 or 800.320.1424 • Fax 208.324.1133